JP2008243577A - Catalyst for polymer solid electrolyte fuel cell, membrane-electrode assembly, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for a fuel cell excelling in both catalyst activity and catalyst stability. <P>SOLUTION: The catalyst for a fuel cell is characterized by comprising metal fine particles represented by the following formula: Pt<SB>x</SB>Ru<SB>y</SB>Si<SB>z</SB>T1<SB>u</SB>, where T1 is at least one kind of element selected from a group comprising Ni, W, V and Mo; x=30-90 at.%; y=0-50 at.%; z=0.5-20 at.%; and u=1-40 at.%, or metal fine particles represented by the following formula: Pt<SB>x</SB>Ru<SB>y</SB>Si<SB>z</SB>T2<SB>u</SB>, where T2 is at least one kind of element selected from a group comprising Hf, Sn, Zr, Nb, Ti, Ta, Cr and AL; x=30-90 at.%; y=0-50 at.%; z=0.5-20 at.%; and u=1-40 at.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell catalyst, and more particularly, to a polymer solid oxide fuel cell catalyst, a membrane electrode assembly using the catalyst, and a fuel cell.

  Solid polymer fuel cells, in particular methanol solid polymer fuel cells using methanol solution as fuel, can be operated at low temperatures and can be reduced in size and weight. Development is underway.

  However, with respect to widespread use, the performance of the conventionally proposed fuel cell is still not sufficient. A fuel cell converts chemical energy into electric power through an electrocatalytic reaction, and a highly active catalyst is indispensable for developing a high-performance fuel cell.

  Until now, PtRu has been generally used as a catalyst for anode electrodes of fuel cells. The voltage loss due to the PtRu catalyst is about 0.3 V compared to the electrocatalytic reaction theoretical voltage of 1.21 V, and a highly active (methanol oxidation activity) anode catalyst exceeding the catalytic ability of PtRu is required. From this point of view, various studies have been made so far, such as adding other elements to PtRu in order to improve the methanol oxidation activity of the PtRu catalyst.

  For example, Patent Document 1 below describes the effect of adding 10 kinds of metals such as tungsten and tantalum, and Patent Document 2 refers to the effect of adding Si, Al, Ti, and the like. However, the reaction field of the catalytic reaction is on the surface of nano-sized catalyst particles, and several atomic layers on the surface of the catalyst almost dominate the catalytic activity. It can change. So far, a solution method such as a dipping method has been generally used for catalyst synthesis, but there is a problem that it is difficult to control the surface of the catalyst for elements that are difficult to be reduced or elements that are difficult to be alloyed.

  On the other hand, catalyst synthesis by sputtering or vapor deposition is advantageous in terms of material control compared to the solution method described above, but changes in conditions such as element type, catalyst composition, substrate material, substrate temperature, etc. At present, the influence on the generation process has not been sufficiently studied. Since the catalyst for a fuel cell is a nanoparticle, the surface electronic state of the catalyst particle and the nanostructure of the particle greatly depend on the type and amount of the additive element. In order to obtain high activity and high stability, the additive element It is thought that it is necessary to optimize the type, amount added, and combination of elements. From such a viewpoint, Patent Document 3 discusses a manufacturing process using a sputtering method, and describes knowledge about elements other than Pt and Ru. Furthermore, Patent Document 4 discloses a catalyst containing a compound selected from silicon, aluminum, and titanium as a catalyst metal.

In any of the above prior arts, the influence of the catalyst composition on the catalyst activity has not yet been sufficiently examined, and it is still possible to provide a fuel cell catalyst having both improved methanol oxidation activity and excellent catalyst stability. It has been requested.
US Pat. No. 3,506,494 JP 2006-278217 A JP 2005-532670 A JP 2006-128118 A

  The present invention has been made in view of the above-described situation in the prior art, and an object of the present invention is to provide a fuel cell catalyst excellent in both catalytic activity and catalyst stability.

In order to achieve the above object, a fuel cell catalyst according to the present invention has the following formula:
Pt _x Ru _y Si _z T1 _u
(However, T1 is at least one element selected from the group consisting of Ni, W, V and Mo, and x = 30 to 90 at.%, Y = 0 to 50 at.%, Z = 0.5 to 20 at.%. %, U = 1 to 40 at.%)
It consists of the metal microparticles represented by these.

  In a preferred embodiment of the present invention, the area of the peak due to the oxygen bond of Si in the spectrum by X-ray photoelectron spectroscopy (XPS) is 200% or less of the area of the peak due to the metal bond of the Si element, more preferably X-ray The area of the peak due to the oxygen bond of the element T1 in the spectrum by photoelectron spectroscopy (XPS) is 200% or less of the peak area due to the metal bond of the element.

Furthermore, the fuel cell catalyst according to the present invention has the following formula:
Pt _x Ru _y Si _z T2 _u
(However, T2 is at least one element selected from the group consisting of Hf, Sn, Zr, Nb, Ti, Ta, Cr and Al, and x = 30 to 90 at.%, Y = 0 to 50 at.%, z = 0.5-20 at.%, u = 1-40 at.%)
It consists of metal microparticles represented by these.

  In the above aspect, preferably, an area of a peak due to an oxygen bond of Si in a spectrum by X-ray photoelectron spectroscopy (XPS) is 200% or less of an area of a peak due to a metal bond of Si element, or an X-ray photoelectron spectroscopy The area of the peak due to the metal bond of the element T2 in the spectrum by (XPS) is 200% or less of the peak area due to the oxygen bond of the element.

  Furthermore, the present invention provides a supported catalyst for a fuel cell in which the above catalyst is supported on a carrier, a membrane electrode assembly provided with the supported catalyst, and a fuel cell provided with the membrane electrode composite. Include.

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst for fuel cells excellent in both catalyst activity and catalyst stability can be provided.

As described above, the fuel cell catalyst according to the first aspect of the present invention has the following formula:
Pt _x Ru _y Si _z T1 _u
(However, T1 is at least one element selected from the group consisting of Ni, W, V and Mo, and x = 30 to 90 at.%, Y = 0 to 50 at.%, Z = 0.5 to 20 at.%. %, U = 1 to 40 at.%)
It consists of the metal microparticles represented by these.

Furthermore, the fuel cell catalyst according to the second aspect of the present invention has the following formula:
Pt _x Ru _y Si _z T2 _u
(However, T2 is at least one element selected from the group consisting of Hf, Sn, Zr, Nb, Ti, Ta, Cr and Al, and x = 30 to 90 at.%, Y = 0 to 50 at.%, z = 0.5-20 at.%, u = 1-40 at.%)
It consists of metal microparticles represented by these.

  That is, the present invention is characterized in that silicon and T element are added in combination to a specific noble metal, and each content ratio is limited to a specific range. By combining the ratios, as shown in the results of Examples and Comparative Examples described later, it was possible to provide a fuel cell catalyst excellent in both catalytic activity and catalyst stability.

  The present invention will be described below together with preferred embodiments.

  In the catalyst of the present invention, Pt is a main catalyst element. Pt is extremely effective for the oxidation of hydrogen and the dehydrogenation reaction of organic fuel, and if the amount of Pt is too low, the catalytic activity is lowered. Therefore, in the above formula, the amount x of Pt is 30 to 90 at. % Is preferable, and x is more preferably 40 to 85 at. % Range. Ru is effective in suppressing CO poisoning, and the amount y of Ru is 0 to 50 at. % Is preferable, and y is more preferably 0 to 45 at. % Range. The catalyst of the present invention can provide a sufficient catalytic activity even if the amount of Ru is low or not contained. Further, the activity may be improved by substituting a part of Pt with another metal. Since noble metals are particularly excellent in chemical stability, it is desirable to substitute them with Rh, Os, Ir or the like.

  In the present invention, Si and T1 element or T2 element (hereinafter, T1 element and T2 element are collectively referred to as T element) function as a promoter. T is at least one element selected from the group consisting of Ni, W, V, Hf, Sn, Zr, Nb, Mo, Ti, Ta, Cr, and Al. In the present invention, as described above, it is possible to add both Si and T elements to the Pt-Ru-based component in a composite manner, and to improve both high activity and high stability harmoniously with this combination. I got the knowledge.

  Although the mechanism of high activation is not necessarily clear, it is considered important that the coexistence of Si element, T element and noble metal is involved in the combination of the above specific compositions, and the catalyst resulting from this The nanostructure, surface structure, and electronic state of the fine particles are presumed to have high activity.

  From such a viewpoint, with respect to Si, the peak area due to the oxygen bond of Si in the catalyst is preferably 200% or less, particularly preferably 150% or less of the peak area due to the metal bond of the Si element. Most preferably, it is 80% or less. In this case, if the area ratio exceeds 200%, the catalytic activity is remarkably lowered, which is not preferable.

  Furthermore, it is important that the T element is in an appropriate element state in order to harmonize both high activity and high stability. From this point of view, for the T1 element (Ni, W, V or Mo element), the peak area due to the oxygen bond of the element in the spectrum by X-ray photoelectron spectroscopy (XPS) is the peak area due to the metal bond of the element. It is desirably 200% or less, particularly preferably 120% or less, and most preferably 80% or less. Furthermore, for the T2 element (Sn, Hf, Zr, Nb, Ti, Ta, Cr or Al element), the peak area due to metal bonding in the spectrum by X-ray photoelectron spectroscopy (XPS) is the peak due to oxygen bonding of the element. The area is particularly preferably 200% or less, particularly preferably 120% or less, and most preferably 80% or less. In both cases, the catalyst activity or stability is improved by setting the area ratio to 200% or less.

  In the present invention, the above-mentioned “peak area” is the integral value of the binding energy axis of the portion obtained by subtracting the signal background from the peak of the element in the XPS spectrum. When there is an overlap of peaks, peak areas belonging to the element can be obtained by performing peak separation.

  In the present invention, the Si amount z in the catalyst is 0.5 to 20 at. %, More preferably 1 to 15 at. % Range. The Si content is 0.5 at. If it is less than 5%, the co-catalyst action of Si is insufficient. When Si is contained in an amount exceeding%, the number of main active sites constituted by Pt and Ru atoms is remarkably reduced, and thus the catalytic activity is lowered.

  Further, in the present invention, the amount of T element u in the catalyst is 0.5 to 40 at. % Is preferable, and more preferably 1 to 30 at. %, Most preferably 1-20 at. % Range. T element amount u is 0.5 to 40 at. If it is out of the range of%, it is difficult to achieve both catalytic activity and stability.

  Furthermore, in the case of containing Sn, the Sn amount is 0.5 to 10 at. %, Most preferably 1-8 at. %. 0.5 at. %, Or 10 at. If Sn is contained in excess of%, Sn's promoter action is reduced.

  Further, in the catalyst of the present invention, at least one kind of metal can be additionally added from the above-mentioned other metal elements, particularly Mn, Fe, Co, Au, Cu, and a composite of these metal elements. Addition may contribute to activity improvement. About addition amount, 2-20 at. % Range is preferred.

  In the catalyst of the present invention, the oxygen content is allowed. In the course of the synthesis process, metal components on the catalyst surface are inevitably oxidized by surface oxidation treatment such as oxygen adsorption or pickling on the catalyst surface when storing the catalyst. It can be seen that power and stability are improved when small amounts of oxide are formed. Therefore, in the present invention, the existence of such an oxide is positively allowed. From such a viewpoint, the oxygen content in the catalyst of the present invention is 15 at. % Or less is desirable. 15 at. On the other hand, if it exceeds%, the catalytic activity is adversely affected.

  In the catalyst of the present invention, 0.1 at. % Of impurities such as P, S, Cl and the like are allowed. These elements may be mixed during the preparation or treatment process of the catalyst or membrane electrode assembly. When the content is less than or equal to%, it is considered that the catalyst of the present invention is hardly deteriorated in characteristics. Also from this point, it is considered that the surface structure of the catalyst in the present invention has high tolerance.

  The particle size of the catalyst according to the present invention is not particularly limited, but the highest activity is obtained when the particles are nano-particles. Therefore, the average particle diameter of the catalyst particles according to the present invention is preferably 10 nm or less. This is because the activity efficiency of a catalyst can be improved by setting it as 10 nm or less. A more preferable average particle size range is 0.5 to 10 nm. By controlling the thickness to 0.5 nm or more, the control of the catalyst synthesis process is facilitated, which is advantageous in terms of cost.

  As the catalyst particles, fine particles having an average particle diameter of 10 nm or less may be used alone, but aggregates (secondary particles) of primary particles made of the fine particles can also be used.

  The present invention also includes a form of a supported catalyst in which the above catalyst is supported on a carrier. In this case, a conductive carrier can be used as the carrier. Examples of the conductive carrier include carbon black. However, the carrier is not limited to this, and a conventionally known carrier can be appropriately used as long as the carrier is excellent in conductivity and stability. In recent years, nanocarbon materials such as fibers, tubes, and coils have been developed. Their surface states are different, and the activity may be further improved by supporting the catalyst particles used in the present invention on these particles. In addition to the carbon material, a conductive ceramic material may be used as the carrier. In this case, a further synergistic effect between the ceramic support and the catalyst particles can be expected.

  Next, a method for producing a supported catalyst according to the present invention will be described. The supported catalyst according to the present invention is produced, for example, by sputtering or vapor deposition. These methods make it easier to produce a catalyst having a specific mixed state having a metal bond, as compared with solution methods such as an impregnation method, a precipitation method, and a colloid method. It is difficult to produce the supported catalyst of the present invention by a known solution method. According to a method in which a polynuclear complex of Pt, Ru and T element having a metal bond is prepared, impregnated in a support, and reduced, it is difficult to synthesize the multinuclear complex, and thus the supported catalyst of the present invention cannot be obtained. In addition, the manufacturing cost is likely to be high. In addition, when the supported catalyst of the present invention is produced by an electrodeposition method or an electrophoresis method, it is expected that the control to nanoparticles becomes difficult and disadvantageous in production cost. When performing a sputtering method or a vapor deposition method, an alloy target may be used, and simultaneous sputtering or simultaneous vapor deposition may be used using each metal target of a constituent element.

  A method for attaching catalyst particles to a conductive carrier by sputtering will be described. First, the particulate or fibrous conductive carrier is sufficiently dispersed. Next, the dispersed carrier is inserted into a holder in a champ of the sputtering apparatus, and the constituent metal of the catalyst is attached to the carrier by sputtering while stirring in a predetermined direction. The carrier temperature during sputtering is desirably set to 400 ° C. or lower. If the set temperature is too high, phase separation may occur in the catalyst particles, and the catalyst activity may become unstable. In order to reduce the cost required for cooling the carrier, the lower limit of the carrier temperature is preferably 10 ° C. The carrier temperature can be measured with a thermocouple. In addition, stirring is important for achieving uniform catalyst adhesion. When the stirring is not performed, the distribution of the catalyst is uneven, and the fuel cell characteristics are deteriorated.

  The catalyst of the present invention can also be obtained by directly sputtering a porous paper containing conductive carbon fibers, an electrode diffusion layer, or an electrolyte membrane. In this case, it is necessary to form the catalyst in the form of nanoparticles by adjusting the process. Moreover, it is desirable that the porous paper temperature be 400 ° C. or lower as in the above. In some cases, the activity may be further improved by forming the catalyst particles by sputtering or vapor deposition and then performing pickling, alkali treatment or heat treatment. This is probably because the catalyst structure or surface structure is further optimized by pickling treatment, alkali treatment or heat treatment. The pickling treatment may be an aqueous acid solution, but an aqueous sulfuric acid solution is preferably used. For the alkali treatment, an aqueous solution of an alkali can be used. About heat processing, it is desirable to process in the atmosphere below 10-400 degreeC and oxygen partial pressure less than 5%. In addition, since fine particles are easily formed, another material such as carbon and a constituent metal element may be sputtered or evaporated at the same time. In the present invention, it is also possible to simultaneously sputter or vapor-deposit a metal having good solubility, such as Cu or Zn, and a constituent metal element, and then remove Cu, Zn or the like by pickling.

  Furthermore, the present invention includes a membrane electrode assembly constituted by using the supported catalyst. A membrane electrode assembly (MEA) according to a preferred embodiment of the present invention includes an anode, a cathode, and a proton conductive membrane disposed between the anode and the cathode.

  In addition, the fuel cell according to the embodiment of the present invention can be configured from the one having the membrane electrode assembly as described above.

  FIG. 1 is a side view schematically showing a fuel cell according to an embodiment of the present invention.

  The membrane electrode assembly (MEA) shown in FIG. 1 includes an anode 1, a cathode 2, and a proton conductive membrane 3. The anode 1 includes a diffusion layer 4 and an anode catalyst layer 5 laminated thereon. The cathode 2 includes a diffusion layer 6 and a cathode catalyst layer 7 laminated thereon.

  The anode 1 and the cathode 2 are laminated so that the anode catalyst layer 5 and the cathode catalyst layer 7 face each other with the proton conductive membrane 3 interposed therebetween. In FIG. 1, reference numeral 8 indicates an external circuit.

  The anode catalyst layer contains the aforementioned catalyst. On the other hand, for example, Pt can be used for the cathode catalyst included in the cathode catalyst layer. The cathode catalyst may be supported on a carrier, but may be used without being supported. A conductive porous sheet can be used for the diffusion layer. As the conductive porous sheet, for example, a sheet formed of a material having air permeability or liquid permeability such as carbon cloth or carbon paper can be used.

  The proton conductive material contained in the anode catalyst layer, the cathode catalyst layer, and the proton conductive membrane can be used without particular limitation as long as it is a material that can transmit protons. Examples of proton conductive substances include fluorine resins having sulfonic acid groups such as Nafion (manufactured by DuPont), Flemion (manufactured by Asahi Kasei), and Ashiburek (manufactured by Asahi Glass), and inorganic substances such as tungstic acid and phosphotungstic acid. However, it is not limited to these.

  A fuel cell according to an embodiment of the present invention includes the above-described MEA, means for supplying fuel to the anode, and means for supplying an oxidant to the cathode. The number of MEAs to be used may be one or more. By using multiple, higher electromotive force can be obtained. As the fuel, methanol, ethanol, formic acid, or an aqueous solution containing one or more selected from these can be used.

  Hereinafter, the present invention will be described more specifically based on examples of the present invention and comparative examples.

(Examples 1-20, Comparative Examples 1-19)
First, a carbon black carrier (trade name Vulcan XC72, manufactured by Cabot Corporation, specific surface area: about 230 m ² / g) was sufficiently dispersed. Next, the dispersed carrier was placed in a holder in a champ of an ion beam sputtering apparatus, and Ar gas was flowed after the degree of vacuum became 3 × 10 ⁻⁶ Torr or less. While stirring the support while maintaining the temperature at 400 ° C. or lower, sputtering was performed using a metal or an alloy as a target so as to have various compositions shown in Table 1, and catalyst particles were attached to the support. The obtained product was pickled using an aqueous sulfuric acid solution (10 g sulfuric acid, 200 g water), then washed with water and dried.

(Comparative Example 20)
A supported catalyst having the same composition was produced in the same manner as in the example described in Patent Document 2 described above. First, 500 mg of carbon black (trade name Vulcan XC72, manufactured by Cabot Corporation, specific surface area: about 230 m ² / g) is added to 1000 ml of an ethanol solution containing 100 mg of Si, and the mixture is sufficiently stirred and dispersed uniformly. The mixture was heated to 55 ° C. with stirring to volatilize and remove ethanol. Subsequently, while flowing hydrogen gas at a flow rate of 50 ml / min, the residue obtained by the above-described method was heated at 300 ° C. for 3 hours to support vanadium on the carbon black.

  Next, 300 ml of a cyclohexane solution containing 317.7 mg of 1,5-cyclooctadiene dimethylplatinum as a platinum metal amount and 40 ml of an ethanol solution containing 82.3 mg of ruthenium chloride as a ruthenium metal content were mixed. Then, the above Si-supported carbon was added and sufficiently stirred to disperse uniformly, and then heated to 55 ° C. with stirring to volatilize and remove the solvent. Next, while flowing hydrogen gas at a flow rate of 50 ml / min, the residue obtained by the above method is heated at 300 ° C. for 3 hours to support platinum, ruthenium and Si on carbon black, and the supported catalyst is Obtained.

  XPS measurement was performed on the various catalysts using Quantum-2000 manufactured by PHI. Charge-up compensation and charge correction (C1s: C−C = 284.6 eV) using a neutralizing gun (electron gun, argon gun) were performed. Table 2 shows the identification of peaks due to metal bonds and oxygen bonds of each element. For example, the Si 2p spectrum was used for the Si element, and a peak with a binding energy in the range of 99 to 100 eV was identified by a metal bond, and a peak in the range of 103 to 104 eV was identified based on an oxygen bond. When there are multiple types of T element contained in the catalyst particles, the T element with the largest content is defined as the main T element, and the measurement result of the main T element (T1 element or T2 element) of each catalyst Table 1 shows.

  The peak area ratio of the main T1 element is the peak area due to oxygen bonding when the peak area due to metal bonding of the same element is 100%, and the peak area ratio of the main T2 element is 100% due to oxygen bonding of the same element. % As the peak area due to metal bonding.

  As shown in Table 1, the peak area due to oxygen bonding of each main T1 element on the XPS spectra of Examples 1 to 20 is 200% or less of the peak area due to metal bonding of the same element, and the metal of each main T2 element It was confirmed that the peak area due to elementary bonds was 200% or less of the peak area due to oxygen bonds of the same element. It was found that the Si element of Comparative Example 20 produced by the solution method was almost in an oxidized state. The sample for the above measurement is a pickled catalyst. The catalyst before pickling may have a higher peak of oxidative bond than the pickled one, but it is often due to an unstable oxide layer, and if the pickling process is not performed, it will naturally become a stable layer even during power generation. It changed, and it was confirmed that the area ratio of the peak due to the oxidative bond was the same as that of the pickled catalyst.

  Regarding the average particle diameter of the catalyst particles of each supported catalyst, TEM observation is performed for any five different visual fields, the diameter of 20 particles is measured in each visual field, and the average of the diameters of 100 particles in total is the average particle diameter. As shown in Table 1 below.

  Examples 1 to 20 and Comparative Examples 1 to 20 are anode catalysts, each of which is combined with a standard cathode electrode (carbon black-supported Pt catalyst: manufactured by Tanaka Kikinzoku Co., Ltd.) as follows. A body and a single cell are produced and evaluated.

<Anode electrode>
3 g of the obtained various catalysts were weighed. These supported catalysts, 8 g of pure water, 15 g of 20% Nafion solution, and 30 g of 2-ethoxyethanol were thoroughly stirred and dispersed, and a slurry was prepared. The above slurry was applied to water-repellent carbon paper (350 μm, manufactured by Toray Industries, Inc.) with a control coater and dried to prepare an anode electrode having a noble metal catalyst loading density of 1 mg / cm ² .

<Cathode electrode>
First, 2 g of Pt catalyst manufactured by Tanaka Kikinzoku Co., Ltd. was weighed, 5 g of pure water, 5 g of 20% Nafion solution, and 20 g of 2-ethoxyethanol were thoroughly stirred and dispersed, and a slurry was prepared. The above slurry was applied to water-repellent carbon paper (350 μm, manufactured by Toray Industries, Inc.) with a control coater and dried to prepare a cathode electrode having a noble metal catalyst loading density of 2 mg / cm ² .

<Production of membrane electrode composite>
The cathode electrode and the anode electrode are each cut into a square of 3.2 × 3.2 cm so that the electrode area is 10 cm ² , and Nafion 117 (manufactured by DuPont) is used as a proton conductive solid polymer membrane between the cathode electrode and the anode electrode. ) And thermocompression bonded at a pressure of 30 kg / cm ² at 125 ° C. for 10 minutes to prepare a membrane electrode assembly.

A single cell of a fuel direct supply type polymer electrolyte fuel cell was fabricated using the membrane electrode assembly and the flow path plate. In this single cell, a 1M aqueous methanol solution as a fuel, a flow rate of 0.6 ml / min. In addition to supplying the cathode electrode with air at a flow rate of 200 ml / min to the cathode electrode, 100 mA / cm ² current density was discharged with the cell maintained at 50 ° C., and the cell voltage after 30 minutes was measured. The results are shown in Table 1 below. For high stability, a single cell was generated for 500 hours under the above operating conditions, and the voltage decrease rate at 100 mA / cm ² current density was evaluated as an index. The results are shown in Table 1 below.

  As shown by the results in Table 1, when Examples 1 to 20 and Comparative Example 1 are respectively compared, it can be seen that the catalyst of the present invention has higher fuel cell characteristics than the PtRu catalyst and the same stability as the PtRu catalyst. Further, when Examples 1 to 20 and Comparative Examples 2 to 14 are respectively compared, it is understood that high fuel cell characteristics and high stability cannot be achieved by adding Si or T element alone. By comparing Examples 1 and 2 with Comparative Examples 15 to 19, respectively, the amount of Si element added was 0.5 to 20 at. %, Or the addition amount of Ni element is 1 to 40 at. It can be seen that when it is out of the range of%, it is impossible to achieve both high activity and high stability with a deterioration rate of 1% or less. Similar results were obtained for other elemental systems. Comparing Example 1 and Comparative Example 20, it can be seen that in order to obtain high activity, it is necessary to control the bonding state of elements by the process in addition to the composition.

  The same tendency as described above was confirmed for the reformed gas type polymer electrolyte fuel cell using the catalyst of the present invention. Therefore, the catalyst of the present invention is more effective than conventional Pt-Ru catalysts for CO poisoning.

1 is a side view schematically showing a fuel cell according to an embodiment of the present invention.

Explanation of symbols

1 Anode 2 Cathode 3 Proton Conductive Membrane 4 Diffusion Layer 5 Anode Catalyst Layer 6 Diffusion Layer 7 Cathode Catalyst Layer 8 External Circuit

Claims (9)

Following formula:
Pt _x Ru _y Si _z T1 _u
(However, T1 is at least one element selected from the group consisting of Ni, W, V and Mo, and x = 30 to 90 at.%, Y = 0 to 50 at.%, Z = 0.5 to 20 at.%. %, U = 1 to 40 at.%)
The catalyst for fuel cells characterized by comprising the metal microparticles represented by these.   2. The fuel cell catalyst according to claim 1, wherein an area of a peak due to an oxygen bond of Si in a spectrum obtained by X-ray photoelectron spectroscopy (XPS) is 200% or less of an area of a peak due to a metal bond of an Si element.   2. The fuel cell catalyst according to claim 1, wherein an area of a peak due to an oxygen bond of the element T <b> 1 in a spectrum by X-ray photoelectron spectroscopy (XPS) is 200% or less of a peak area due to a metal bond of the element. Following formula:
Pt _x Ru _y Si _z T2 _u
(However, T2 is at least one element selected from the group consisting of Hf, Sn, Zr, Nb, Ti, Ta, Cr and Al, and x = 30 to 90 at.%, Y = 0 to 50 at.%, z = 0.5-20 at.%, u = 1-40 at.%)
The catalyst for fuel cells characterized by comprising the metal microparticles represented by these. The fuel cell catalyst according to claim 4, wherein an area of a peak due to an oxygen bond of Si in an X-ray photoelectron spectroscopy (XPS) spectrum is 200% or less of an area of a peak due to a metal bond of an Si element.   The catalyst for a fuel cell according to claim 4, wherein an area of a peak due to a metal bond of the element T2 in a spectrum by X-ray photoelectron spectroscopy (XPS) is 200% or less of an area of a peak due to an oxygen bond of the element.   A supported catalyst for a fuel cell, wherein the catalyst according to any one of claims 1 to 6 is supported on a carrier.   A membrane electrode assembly comprising the supported catalyst according to claim 7.   A fuel cell comprising the membrane electrode assembly according to claim 8.

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